Can I ask for some help on what mesh and texture/addon scenery to buy (payware or freeware)? I am mainly interested in something of high detail and quality to look as realistic as possible and beauthiful to with auto-gen support. Would be good if it is for the whole world but otherwise USA and south America would be my priorities.

Ground Environment X covers all of the USA and Canada, so that might be what you are looking for. You can also get the North America Mesh from FSGenesis to go along with it, which includes 10m mesh for USA and 20m for Canada. If you are getting GEX its best to get UTX as well.

GEX + UTX + 10m Mesh is currently the best way to go for North America.

Here's what chicago looks like with GEX + UTX. Read pages 62 through 64 of this thread for more info and comparison images.